You bought a seat.. put the car seat on the plane.. it will be just like being in a car.. it will keep her pinned in (in a good way) ..
Books are good.
Coloring books
anything snacks that can be transfered from bag to bag or continer to continer.
Get a tray for the car seat, from experience the tray on the plane does not go down with the car seat there.
some kind of interactive game.. We have the alpabit apple. My daughter will sit and play with that for a while.
Get a new toy, something that they have not seen yet or seen in a while. They will capitave thier attn. longer.
Relax. there are two type of people in this world.. Parents and non.. Most parents are going to be paitent .. some non will be as well.. :)
Most planes have 3 seats to a row ( well the ones we fly on do anyway) We are flying Saturday with a 4.5 year old and 20 month old.. we got one seat.. the 20 month old will be on my lap.. so we can all sit in the same row.
Paci, bottles etc.. for take off and landing. or have them eat.. something chewie.. so they are chewing and swallowing.
security- you are allowed to bring enough bottles /milk for the trip and then some. I breast fed last year when we flew and had no issues brining liquid or frozen breast milk.
extra outfits for all incase of tummy issues.
Relax and have fun!